JPH09194673A - Acrylic resin composition for artificial marble and method for producing artificial marble - Google Patents

Abstract

(57) Abstract: A high-quality artificial marble is easily and efficiently produced by press molding of an acrylic resin composition. SOLUTION: This comprises 42 to 65% by weight of a vinyl monomer mainly composed of methyl methacrylate, 1 to 8% by weight of a crosslinking agent, and 27 to 50% by weight of a carboxyl group-containing methyl methacrylate polymer having an average molecular weight of 10,000 to 150,000. , Acid number 5
20 to 20 parts by weight of acrylic syrup, 0.5 to 1.5 parts by weight of a curing agent and 0.01 to 0.
3 parts by weight, 1 to 4 parts by weight thickener, 1 to 5 parts by weight internal release agent, 120 to 250 parts by weight filler and 1 to 2 reinforcing fibers.
An acrylic resin composition for artificial marble, which is obtained by mixing 0 part by weight. This acrylic resin composition was molded at a molding temperature of 105 to 14
0 ° C., temperature difference between the front surface and the back surface of the molded product 10 to 20 ° C., mold clamping speed 1 to 8 mm / sec, molding pressure 3 to 10 MPa
Then, in the final 5 to 30 seconds of mold clamping, vacuum deaeration is performed and press molding is performed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an acrylic resin composition capable of easily and efficiently producing high-quality artificial marble by press molding, and a method for producing artificial marble using this acrylic resin composition.

[0002]

2. Description of the Related Art Acrylic resins, together with unsaturated polyester resins, are the main materials for artificial marble. At present, however, only the cast molding is carried out and the press molding is carried out in the manufacture of the acrylic resin artificial marble. Absent. Therefore, shortening the molding cycle during mass production has been an issue. That is, in the case of molding a molded product equivalent to 40 kg, the molding cycle from metering, stirring, casting, molding, and demolding in cast molding requires 1 to 2 hours. On the other hand, in the case of press molding, the molding cycle of weighing, stirring, molding, and demolding is 20 to 40 minutes, and the molding cycle is shortened to 1/2 to 1/5 of the case of cast molding.

Further, since press molding is carried out at higher temperature and higher pressure than cast molding, there is an advantage that the degree of curing of the obtained molded product is high and a more stable cured product can be obtained.

As described above, the press molding has an advantage that the molding cycle is faster than the cast molding, the mass productivity is excellent, and the curing is stable under high temperature and high pressure, so that the quality is stable and the working environment is good. However, the following are technical factors that have not been conventionally press-molded with an acrylic resin.

It is difficult to increase the viscosity of acrylic syrup (a methyl methacrylate polymer (PMMA) dissolved in a methyl methacrylate monomer (MMA)) as a main molding raw material.

The shrinkage rate is high (the volumetric shrinkage rate of the MMA monomer at the time of curing is 21%), and molding is difficult. The curing reaction is faster than that of unsaturated polyester (Δ
T / Δt (heat generation / time) is high), and its control is difficult in high temperature molding.

The boiling point of the monomer is low (the boiling point of MMA is 100 ° C.), and the molding temperature, the mold clamping speed, and the degree of vacuum are limited. It is sensitive to curing inhibition by oxygen, and even the presence of micro bubbles causes a large uncured portion.

With respect to the above factors, it has been conventionally proposed that an acid value is imparted to a polymer component to obtain a thickening effect of MgO as a thickener (Japanese Patent Publication No. Sho 64).
-11652, Japanese Patent Laid-Open No. 62-146930, Japanese Patent Publication No. 1-46530, Japanese Patent Publication No. 3-4109.
No. 7, JP-A-4-23818).

[0009]

However, since other factors are not solved, the press molding of acrylic resin has not yet been industrially carried out.

The present invention has been made in view of the above conventional circumstances, and an acrylic resin composition and an acrylic resin composition capable of easily and efficiently producing high-quality artificial marble by press molding. It is an object of the present invention to provide a method for producing an artificial marble used.

[0011]

The acrylic resin composition for artificial marble of the present invention comprises 42 to 65% by weight of a vinyl monomer containing methyl methacrylate as a main component, 1 to 8% by weight of a crosslinking agent, and an average molecular weight of 1 0.5 to 1.5 parts by weight of a curing agent per 100 parts by weight of an acrylic syrup having an acid value of 5 to 20 containing 27 to 50% by weight of a carboxyl group-containing methyl methacrylate polymer of 10,000 to 150,000 and polymerization. 0.005 to 0.3 parts by weight of inhibitor, 1 to 4 parts by weight of thickener, 1 to 5 parts by weight of internal release agent, 120 to 250 parts by weight of filler, and 1 to 20 parts by weight of reinforcing fiber are mixed. It is characterized by

The method for producing artificial marble of the present invention is
The acrylic resin composition of the present invention is molded at a molding temperature of 105-
140 ° C, temperature difference between the front surface and the back surface of the molded product 10 to 20
C, mold clamping speed 1 to 8 mm / sec, molding pressure 3 to 10 M
It is characterized by performing vacuum deaeration and press molding in the last 5 to 30 seconds of mold clamping with Pa.

The mechanism of action of the acrylic resin composition for artificial marble of the present invention is as follows.

(I) To increase the viscosity of the acrylic syrup, an acid value is given to the polymer component to increase the viscosity. (ii) With respect to the above shrinkage problem, the monomer fraction of the acrylic syrup is reduced as much as possible, and the molecular weight of the polymer is reduced within a range allowed by the physical properties after curing so that the viscosity of the acrylic syrup does not increase. Further, the shrinkage ratio of the entire composition is lowered by increasing the blending amount of the reinforcing fiber and the filler.

Further, in the method for producing an artificial marble of the present invention, the following improvements are aimed at. (iii) With respect to the above-mentioned problem of premature curing, there is no fear of foaming even if ΔT / Δt is high under pressurization, but defects are avoided by minimizing the mold temperature distribution. (iv) Regarding the restrictions on the molding conditions described above, vaporization can be prevented even when the molding temperature is higher than the boiling point of the monomer under press-pressurization.Therefore, the tightening time from charge to pressurization, the molding temperature, and the vacuum release. Avoid evaporation by devising the molding conditions such as the timing of the qi. (v) With respect to the above-mentioned inhibition of curing, bubble-free molding is performed by devising a charge pattern or vacuum deaeration, or devising a mold structure such as discharging the end portion, which tends to contain bubbles, as burr.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

First, the acrylic syrup which is the main constituent of the acrylic resin composition of the present invention will be described.

The acrylic syrup according to the present invention is a vinyl monomer whose main component is methyl methacrylate: 42
-65 wt% Crosslinking agent: 1-8 wt% Carboxyl group-containing methyl methacrylate polymer having an average molecular weight of 10,000-150,000: 27-50 wt% and an acid value of 5-20.

When the proportion of the vinyl monomer is less than 42% by weight or the proportion of the carboxyl group-containing methyl methacrylate polymer is more than 50% by weight, the shrinkage rate at the time of molding becomes small, but the syrup viscosity is high, and therefore the handling is difficult. Becomes difficult. Conversely, the proportion of vinyl monomer is 65% by weight
When the ratio is more than 100% or the ratio of the carboxyl group-containing methyl methacrylate polymer is less than 27% by weight, the cured product properties are improved, but the shrinkage ratio during molding is increased.

Further, when the average molecular weight of the carboxyl group-containing methyl methacrylate polymer is less than 10,000, the cured physical properties deteriorate, and conversely, when it exceeds 150,000, the shrinkage increases.

That is, in the present invention, the viscosity is increased by decreasing the molecular weight of the carboxyl group-containing methyl methacrylate polymer and increasing the compounding ratio of the carboxyl group-containing methyl methacrylate polymer within the range where the physical properties after curing satisfy the required performance. Reduces shrinkage without affecting. Generally, the average molecular weight of the carboxyl group-containing methyl methacrylate polymer is 10,000 to
150,000, the proportion of carboxyl group-containing methyl methacrylate polymer is 30 to 45% by weight, and the viscosity is 10,000 to 200,000 cps.
(Viscosity increases as the amount of polymer added increases) and shrinkage (volume) of 10 to 15% can be realized.

The acrylic syrup of the present invention is thickened by a combination of a methyl methacrylate polymer having an acid value and a thickening agent such as MgO.
The acid value of the acrylic syrup of the present invention must be in the range of 5-20. If the acid value is less than 5, thickening will be insufficient, and if the acid value exceeds 20, the water resistance and yellowing resistance of the obtained product will be reduced.

The cross-linking agent is effective in improving the heat resistance and chemical resistance of the product after curing, but if the ratio is less than 1% by weight, the effect of addition is insufficient, and if it exceeds 8% by weight, a cured product is obtained. Becomes brittle, which is not preferable. As the cross-linking agent, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, dimethylolethane dimethacrylate, 1,1-
Such as dimethylolpropane dimethacrylate, 2,2-dimethylolpropane dimethacrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane dimethacrylate Polyfunctional acrylates and polyhydric esters of (meth) acrylic acid with polyhydric alcohols such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, pentaerythritol, dipentaerythritol, divinylbenzene, triaryl isocyanurate, aryl Methacrylate etc. are mentioned. Among them, polyfunctional acrylates such as 1,6-hexanediol dimethacrylate are preferable.

In the present invention, the vinyl monomer is mainly composed of methyl methacrylate, but when the proportion of methyl methacrylate in the vinyl monomer is less than 50% by weight, weather resistance and stain resistance of the artificial marble obtained are obtained. Therefore, the proportion of methyl methacrylate in the vinyl monomer is 50% by weight or more, preferably 75% by weight or more.

Examples of vinyl monomers that can be used in combination with methyl methacrylate include (meth) acrylic acid esters having an alkyl group having 1 to 20 carbon atoms, cyclohexyl (meth) acrylate, glycidyl (meth) acrylate and hydroxyalkyl (meth). ) Acrylate, (meth) acrylic acid, (meth) acrylic acid metal salt, fumaric acid, fumaric acid ester, maleic acid, maleic acid ester, aromatic vinyl, vinyl acetate, (meth) acrylic acid amide, (meth) acrylonitrile, Examples thereof include vinyl chloride and maleic anhydride.

The carboxyl group-containing methyl methacrylate polymer according to the present invention comprises methyl methacrylate and
Obtained by copolymerizing with an unsaturated carboxylic acid, where the unsaturated carboxylic acid is acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid monoalkyl ester, maleic acid. Monobasic acid such as monoalkyl ester and fumaric acid monoalkyl ester, dibasic acid or monoalkyl ester of dibasic acid, and hydroxyl group-containing vinyl monomers such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate , Hydroxypropylmethacrylate, hydroxybutylmethacrylate and the like and dibasic acid or tribasic acid anhydride, for example, succinic anhydride, phthalic anhydride, hexahydrophthalic anhydride,
Unsaturated carboxylic acids obtained by ring-opening addition reaction of tetrahydrophthalic anhydride, nadic acid anhydride, trimellitic anhydride, etc. are used.

As the constituent components other than methyl methacrylate and the unsaturated carboxylic acid of the carboxyl group-containing methyl methacrylate polymer according to the present invention, the above-mentioned monomers used as vinyl monomers can be applied as they are. .

Further, in the acrylic syrup, in addition to the vinyl monomer, the cross-linking agent and the carboxyl group-containing methyl methacrylate polymer, a polymerization inhibitor represented by quinones, hydroquinones (polyhydric phenols) and the like is added in an amount of 0.5. You may mix | blend with less than weight%, and the effect of improving storage stability is acquired by this.

The acrylic resin composition for artificial marble of the present invention uses the above acrylic syrup in the following composition.

Acrylic syrup: 100 parts by weight Curing agent: 0.5 to 1.5 parts by weight Polymerization inhibitor: 0.01 to 0.3 parts by weight Thickener: 1 to 4 parts by weight Internal release agent: 1 to 5 parts by weight Filler: 120 to 250 parts by weight Reinforcing fiber: 1 to 20 parts by weight If the ratio of the curing agent to 100 parts by weight of acrylic syrup is less than 0.5 parts by weight, curing becomes poor, and if it exceeds 1.5 parts by weight, the surface becomes It will hurt or the performance will decrease. As the curing agent, a peroxyester type one such as t-butylperoxy-2-ethylhexanoate is used. It is possible to suitably control the curing reaction by using a combination of a curing agent having a fast curing reaction and a curing agent having a slow curing reaction.

When the ratio of the polymerization inhibitor to 100 parts by weight of acrylic syrup is 0.01 parts by weight or more than 0.3 parts by weight, the rise of the curing reaction is poorly adjusted.
As the polymerization inhibitor, methyl tert-butyl hydroquinone, methoxyquinone or the like can be used.

If the ratio of the thickener to 100 parts by weight of acrylic syrup is less than 1 part by weight, the thickening effect is insufficient, and if it exceeds 4 parts by weight, the compound becomes yellow. As the thickener, an oxide or hydroxide of a divalent metal such as magnesium, calcium, zinc or strontium, preferably magnesium oxide (MgO) is used.

If the ratio of the internal release agent to 100 parts by weight of acrylic syrup is less than 1 part by weight, a sufficient addition effect cannot be obtained, and if it exceeds 5 parts by weight, the weather resistance becomes poor. As the internal mold release agent, zinc stearate, calcium stearate or the like can be used.

In the present invention, the shrinkage ratio is reduced by adding a high amount of filler. If the ratio of the filler to 100 parts by weight of acrylic syrup is less than 120 parts by weight, the effect of reducing shrinkage cannot be sufficiently obtained, and if it exceeds 250 parts by weight, curing inhibition occurs. As the filler, calcium carbonate, barium sulfate, talc, silica, alumina, aluminum hydroxide, glass spheres, etc., especially aluminum hydroxide with high secondary processability for artificial marble for counters, water resistant for artificial marble for bathtubs. Silica with good properties and surface hardness is used, and the average particle size is usually 0.1 to 100 μm,
Preferably 0.5 to 50 μm, more preferably 1 to 30
μm. If the average particle size exceeds 100 μm, unclear and fine spots may appear on the resulting artificial marble, which may impair the appearance. If the average particle size is less than 0.1 μm,
The transparency may be lost or the filling amount may be limited.

The reinforcing fiber exerts a reinforcing effect and a shrinkage reducing effect, but if the ratio of the reinforcing fiber to 100 parts by weight of acrylic syrup is less than 1 part by weight, this effect cannot be sufficiently obtained, and 20 parts by weight is required. If it exceeds, the smooth surface of the artificial marble will be lost. As the reinforcing fiber, glass fiber, carbon fiber, or organic fiber can be used, the average fiber length of which is 500 μm to 25 mm, and the average fiber diameter of which is 10 to 15 μm.
It is preferred that

If necessary, other ultraviolet absorbers, defoaming agents, surface treatment agents and the like may be added to the acrylic resin composition for artificial marble of the present invention.

Next, the method for producing the artificial marble of the present invention will be described.

In the method of the present invention, the acrylic resin composition of the present invention as described above is used at a molding temperature of 105 to 140.
C., the temperature difference between the front surface and the back surface of the molded product is 10 to 20.degree. C., the mold clamping speed is 1 to 8 mm / sec, and the molding pressure is 3 to 10 MPa. Mold.

Regarding the molding temperature, since the boiling point of methyl methacrylate is as low as 100.degree. C., it is not preferable to set the temperature above 140.degree. Generally, the temperature of the existing press die is adjusted by steam, so the molding temperature is 105
C. to 140.degree. C., and within this molding temperature range, the temperature difference between the front surface side and the back surface side of the product is 10.degree. C. to 20.degree. C. (the back surface side is lower than the front surface side).

The mold clamping speed is set to 1 to 8 mm / sec so that the time from charging to completion of pressurization is about 30 seconds in consideration of vaporization of methyl methacrylate. With this mold clamping speed, conspicuous volatilization of methyl methacrylate can be avoided.

The molding pressure is 3 to 10 MPa as in the case of unsaturated polyester.

If the vacuum deaeration at the time of mold clamping is excessively strong, vaporization of methyl methacrylate may occur significantly, so that the vacuum deaeration is quickly performed in the last 5 to 30 seconds of mold clamping.

In practicing the present invention, it is preferable to prevent the curing from being hindered by the bubbles by devising the mold structure such as discharging the burr which tends to contain bubbles as a burr.

[0044]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 to 5 and Comparative Examples 1 to 6 Acrylic resin compositions having the formulations shown in Table 1 were prepared using the acrylic syrups having the formulations shown in Table 1, and the following molding conditions were used using the acrylic resin compositions. It was press molded with.

Molding conditions Molding temperature: 135 ° C. (product front side) / 120 ° C. (product back side) Mold clamping speed (final mold clamping speed): 5 mm / sec Molding time: 7 minutes Molding pressure: 5 MPa Vacuum degassing: Mold It took about 10 seconds at the end of tightening.

The molding raw materials used are as follows.

Vinyl-based monomer: Methyl methacrylate monomer Cross-linking agent: Polyfunctional acrylate (ethylene glycol dimethacrylate) Methyl methacrylate polymer I: Carboxyl group-containing methyl methacrylate polymer (average molecular weight 60,000, acid value 2
2.9) Methyl methacrylate polymer II: Methyl methacrylate polymer (average molecular weight 60,000, acid value 0) Methyl methacrylate polymer III: Carboxyl group-containing methyl methacrylate polymer (average molecular weight 60,000, acid value 7)
1.4) Methyl methacrylate polymer IV: carboxyl group-containing methyl methacrylate polymer (average molecular weight 180,000, acid value 2
6.7) Methyl methacrylate polymer V: Carboxyl group-containing methyl methacrylate polymer (average molecular weight 90,000, acid value 16) Methyl methacrylate polymer VI: Carboxyl group-containing methyl methacrylate polymer (average molecular weight 20,000, acid value) Two
0) Curing agent: t-butylperoxy-5,5,5-trimethylhexanoate Polymerization inhibitor: Methyl tertiary butyl hydroquinone Thickener: Magnesium oxide Internal mold release agent: Zinc stearate Filler: Aluminum hydroxide ( Reinforcing fiber: glass fiber (average fiber length 6 mm, average fiber diameter 12 μm)

[0049]

[Table 1]

As a result, in Examples 1 to 5, it was possible to manufacture high-quality artificial marble having a good appearance.

On the other hand, in Comparative Example 1 in which an acrylic syrup containing no carboxyl group and having an acid value of 0 is used, the degree of freedom in the shape of the product to be press-molded is greatly limited due to insufficient thickening. On the contrary, in Comparative Example 2 in which acrylic syrup having a large acid value was used, the artificial marble obtained had yellowing and was inferior in water resistance. Further, in Comparative Example 3 in which the carboxyl group-containing methyl methacrylate polymer has a large average molecular weight, the shrinkage during molding is large, and conversely, in Comparative Example 4 in which the average molecular weight is small, molding is possible, but the heat resistance and mechanical strength are extremely low, None of them produced good products. Furthermore,
In Comparative Example 5 in which the proportion of the carboxyl group-containing methyl methacrylate polymer in the acrylic syrup is small, the shrinkage at the time of molding is large, and in contrast, in Comparative Example 6 in which the proportion is large, it is difficult to mix the compound with high viscosity, None of them produced good products.

[0052]

As described in detail above, according to the acrylic resin composition for artificial marble and the method for producing artificial marble of the present invention, high quality artificial marble can be easily and efficiently produced by press molding. . Therefore, the production efficiency of the artificial marble and the quality of the obtained product are significantly improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C08K 3/00 C08K 3/00 5/09 5/09 (72) Inventor Hiroshi Kato Tokoname City, Aichi Prefecture Koi Ehonmachi 5-chome 1 Inax Co., Ltd. (72) Inventor Takeo Konishi 4-60 Sunadabashi, Higashi-ku, Nagoya, Aichi Prefecture Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Yoshiji Matsumoto East, Nagoya City, Aichi Prefecture 4-60 Sunadabashi, Ku, Mitsubishi Rayon Co., Ltd. Product Development Laboratory (72) Inventor Yujiro Yoshii 4-chome, Sunadabashi 4-chome, Higashi-ku, Nagoya, Aichi Prefecture Mitsubishi Rayon Co., Ltd. (72) Inventor Yuichi Matsuyama 4-60 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi Mitsubishi Rayon Co., Ltd. Product Development Laboratory

Claims (2)

[Claims] 1. A vinyl monomer 42-65% by weight containing methyl methacrylate as a main component, a cross-linking agent 1-8% by weight, and a carboxyl group-containing methyl methacrylate polymer 27-50% by weight having an average molecular weight of 10,000-150,000. % To 100 parts by weight of an acrylic syrup having an acid value of 5 to 20, a curing agent of 0.5 to 1.5 parts by weight, a polymerization inhibitor of 0.0
05-0.3 parts by weight, 1 to 4 parts by weight of a thickening agent, 1 to 5 parts by weight of an internal release agent, 120 to 250 parts by weight of a filler, and 1 to 20 parts by weight of a reinforcing fiber, which is an acrylic for artificial marble. Resin composition. 2. The acrylic resin composition for artificial marble according to claim 1, wherein the molding temperature is 105 to 140 ° C., the temperature difference between the front surface and the back surface of the molded product is 10 to 20 ° C., and the mold clamping speed is 1 to 8 mm.
/ Sec, molding pressure 3 to 10 MPa, the last 5 to mold clamping
A method for producing an artificial marble, which comprises vacuum degassing for 30 seconds and press-molding.